Method for the preparation of styrene polymer foam and foam prepared thereby

Abstract

Styrene polymer foam is prepared using a mixed blowing agent of carbon dioxide plus ethyl chloride and optionally a fluorocarbon to provide a foam having primary cells and secondary cells formed in the struts and walls.

What is claimed is: 
     
       1. A process for the preparation of an alkenyl aromatic thermoplastic resinous elongate foam body having a machine direction and a transverse direction, the body defining a plurality of closed noninterconnecting gas-containing primary cells therein, the steps of the method comprising heat plastifying an alkenyl aromatic synthetic resinous material, adding to the heat plastifying synthetic resinous material a volatile fluid foaming agent to provide a foaming agent resinous polymer mixture under a pressure sufficiently high that foaming is prevented, mixing the fluid foaming agent with the plastified resin to form a blowable resinous mixture, reducing the temperature of the mixture to a temperature such that when pressure is removed therefrom, a foam of desirable quality is obtained, reducing the pressure on the mixture to thereby cause the mixture to form a foam of desired quality, the improvement which comprises employing a blowing agent mixture of from about 3-45 weight percent of carbon dioxide, from 5-97 weight percent ethyl chloride and from about 0-90 weight percent of a fluorocarbon member selected from the group consisting of dichlorodifluoromethane, 1-chloro-1,1-difluoroethane and mixtures thereof, the blowing agent mixture being utilized at a level of about 3-18 parts per 100 parts of resinous material. 
     
     
       2. The process of claim 1 employing in the blowing agent mixture from about 3-25 weight percent of carbon dioxide. 
     
     
       3. The process of claim 1 wherein the blowing agent mixture comprises from about 5-60 weight percent of ethyl chloride. 
     
     
       4. The process of claim 1 employing in the blowing agent mixture from about 30-90 weight percent of fluorocarbon member. 
     
     
       5. The process of claim 1 employing in the blowing agent mixture from about 0-25 weight percent of fluorocarbon member. 
     
     
       6. The process of claim 1 wherein the blowing agent mixture comprises from about 3-25 weight percent carbon dioxide, from about 5-60 weight percent ethyl chloride and from about 30-90 weight percent of fluorocarbon member. 
     
     
       7. The process of claim 1 employing as a blowing agent mixture from about 3-45weight percent carbon dioxide, from about 60-90 weight percent ethyl chloride and from about 0-25 weight percent fluorocarbon member.